PVP: Player Versus Player. Normally in video games all the enemies you have to fight are generated and controlled by the game. In PVP you are fighting against over players. Many games have specific areas that are designated PVP, or you can instigate a one on one fight by inviting another player to duel, but otherwise players are unable to attack other players.

Warsong Gulch is an example of Team PVP. Here you can only attack members of the opposing team.